Schedule 1-A deductions calculator: tips, overtime, car loan, seniors

Schedule 1-A packs four unrelated deductions — tips, overtime, car loan interest and an extra amount for seniors — onto one form, and each one phases out on its own schedule once modified adjusted gross income crosses a threshold. This calculator runs all four phase-outs at once, using the exact caps, thresholds and rounding rules printed on the 2026 draft Schedule 1-A and the final 2025 form, which our companion guide to what changed between the 2025 and 2026 versions walks through line by line.

What the calculator is computing

Each of the four parts follows the same basic shape: cap the qualifying amount, then subtract a reduction that grows with how far modified adjusted gross income sits above a threshold. For tips and overtime, the reduction is $100 for every $1,000 of MAGI over the threshold, rounded down. For car loan interest, it is $200 for every $1,000 over a separate, higher threshold — rounded up, not down. For the senior deduction there is no $1,000 stepping at all; instead, the $6,000 base amount shrinks continuously by 6 cents for every dollar of MAGI over the threshold, and married couples where both spouses qualify get two separate $6,000 bases rather than one shared amount. The calculator applies each rule exactly as printed, then adds the four results together and reports which line of the schedule — and which line of Form 1040 — the total lands on for the year you selected.

Where the constants come from

Every cap and threshold in the calculator is copied directly from the form itself, not estimated or projected. The $25,000 tips cap, the $12,500 ($25,000 married filing jointly) overtime cap, the $10,000 car loan interest cap and the $6,000 senior base appear on both the 2025 final Schedule 1-A and the 2026 draft without change. The MAGI thresholds — $150,000 ($300,000 MFJ) for tips and overtime, $100,000 ($200,000 MFJ) for car loan interest, and $75,000 ($150,000 MFJ) for seniors — are equally unchanged between the two years. None of these figures are indexed to inflation the way the numbers in our IRS 2027 inflation adjustments tracker are, so a future year’s version of this calculator will only need new line numbers, not new dollar figures, unless Congress rewrites the statute.

The asymmetric rounding, and why it matters

Look closely at the instructions on the draft and you will find two different rounding directions in the same schedule. The tips and overtime instructions say to divide the MAGI excess by $1,000 and, if the result is not a whole number, "decrease the result to the next lower whole number." The car loan interest instructions say the opposite: "increase the result to the next higher whole number." Rounding down before multiplying by $100 leaves slightly more of the tips or overtime deduction intact; rounding up before multiplying by $200 removes slightly more of the car loan interest deduction. On a MAGI excess of exactly $3,050, for example, tips or overtime would round the divisor down to 3, while car loan interest rounds the same $3,050 up to 4 — a real difference in the resulting deduction that only shows up because the two parts of the same form round in opposite directions.

What the calculator does not model

A few things sit outside its scope on purpose. It does not check whether tip income was earned in an occupation the IRS treats as customarily tipped, and it does not evaluate whether hours paid at a premium rate meet the Fair Labor Standards Act definition of qualified overtime — both are eligibility tests in the form’s instructions, not arithmetic, and this tool assumes the amounts you enter have already cleared them. It applies the married-filing-separately disqualification the form states for Parts II, III and V, but it does not attempt to split a shared vehicle’s interest between two separately filing spouses, since the form itself is silent on how that would work. And it does not estimate how a smaller taxable income from these deductions changes your withholding or your estimated tax payments — for that interaction, our guide to how AGI moves through the rest of Form 1040 is the place to keep working from the number this calculator produces.

Reading the result next to the form itself

The line numbers shown update with the year toggle because the 2026 draft renumbers three of the four parts — tips and overtime turned from single entry lines into multi-employer tables, which pushed every later line down. The total’s destination changes too: the 2026 draft sends its line 44 total to Form 1040, 1040-SR, or 1040-NR line 13a, while the 2025 form sends its line 38 total to line 13b on Form 1040 or 1040-SR, and to line 13c on Form 1040-NR. Filers who are working through their very first return with a schedule attached may find the surrounding mechanics — what a schedule is, why it attaches to the 1040 rather than replacing it — easier to place after reading our guide to filing a first tax return.